Abstract
This communication is a preliminary report of studies on the frequency of contraction of voluntary muscle under voluntary innervation.
The muscles studied were the flexors of the forearm, and the problem has been approached from three directions:
1. The frequency of the action currents.
2. The frequency of the sound accompanying muscular contraction.
3. The frequency of the mechanical variations over the surface covering the contracting muscles.
The action currents were registered photographically as excursions of the quartz “string” of a large Einthoven galvanometer, and the results are in consonance with those of Piper, who found the rate to be 47 to 50 variations per second.
The muscle sound was made to register itself as electrical variations by use in connection with the galvanometer of a very delicate microphone, carefully protected against external vibrations and connected with a stethoscope placed over the contracting muscles.
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